Electromagnetic friction-brake more especially intended for the driving and change-speed gear of motor road-vehicles



" tosay Vonly that various changes in the veloclty-ratio'transmitted, comprising a reversal of the driven shaft, can be obtained by means of three circular stationa electro-magnets, G, H and I fixed to t e stationa casing of the gear for the purpose of ho ding stationary when re uired, the sun-wheels E1 H1 and I1 to whic the electro-m ets G, H and I are respectively -allotte Dealing first with the two stationary circular electro-magnets. G and H, they are combined with two coned circular brakeelements T and U held against rotation in the i'xed casing, X of the gear but each movable endwise therein, that is to say movable along the axial line thereof, about which the electro-magnets, the. brake-elements and thev `coperating coned friction surfaces hereinafter referred to are all coaxial. To guide these brake-elements T and U. in their endwise movement i n the casing X and to keepI hem from turning there are feathers T1 1 fixed to the back of the brake-elements and made to be a sliding fit in recesses w 1 ing lengthwise in the wall of the casing X.

In compression between the two lconed I brake-elements are springs such as Y, tendi always to keep them` away from each ot er. Screwed through the exterior of the casing are iny threaded holes therein stops such as Z to regulate the position to which the springs Y can move the said coned brake-elements. These stops can be screwed in or out and can be locked securely by means of lock-nuts Z1 in the .different positions to which they are adjustable.' The` springs Y and stops Z are spaced apart at equal angular intervals around the axis of the shaft A.

Two armatures E1 and H2 are appropriated respectively to the magnets G and H. Each armature is provided with a spring such as e (see the lower part of Fig. 1) in vtension between it and a suitable' pin or abutment b on an extension ew from the Vsun-wheel E1 (or H1) to which therarmathereto.

1 On the armature E1 vis, fixed a coned friction-surface E and on the armature H1 is `fixed a similar 'but oppositely-coned frictionsurface H. Endwise movements of the amature armatures will bring these friction surfaces Es and H1 into and out of contact with the co erating brake-elements T and U.

ttached to an extension from the sunwheel I1 to be controlled by the stationary electro-ma net I is an endwise-movable 10 on sliding pins I, with an attached friction surface W, and in the casing in proximity to the said frictionsurface is a slidable but non-rotatable coned brake-element To with va s ring Yo thrusting it toward an adjustable sto Z". This device is virtually one half o a duplex brake-mechanism such as has been illustrated in relation to the electro-magnets G and H.

The action `of the electro-magnetic friction-brake will now be described with reference to the parts G, E, Es and T. A precisely similar action takes place under the o eration of the other electro-magnets and t erefore will not need to be herein descri'bed. So long as fno current passes through the electro-magnet G, the spring e will hold the armature E2 and frictionsurface E1 at the left-hand limit of its endwise movement in the extension from the sun-wheel E1. But when the electro-magnet G is energized, the armature E2 will be drawn magnetically toward 'itl and there will be a correspondin movement of the coned friction surface appropriated to that armature, toward the coned brake- 'element T that faces it, the part Es coming into contact with and being held frictionally bythe part T against rotation.

It is not only necessary that the face of the armature Ez should come, at the finish of this approach movement, into a position of nearness to the face of the electro-magnet G, but also more particularly that the degree of this nearness should be regulatable precisely while the parts E1 T are kept in contact. This can readily be effected by the adjustable stop Z. For instance, if when the conetfl fl'icton surice Elnand the cont' ous ra e-e ement are An eticllly pulled against one anotlillf'l;r thafnface of the armature E', owing to mal-,adjustment of the surfaces of E' and T, -or vowin -to their wear, is not near enough `to `that o the electromagnet G, or` if, y0u the vother hand, it is too near to it, then the :sto SZ -can be adjusted in or out as the casemay and the parts T, Es and E will thereupon move in company. It is by the movement l'of these three parts in company under "the .joint action o spring Y and adjustable stop Z that the gap between the armature and magnetfaces can be increased or reduced, as may be required. The gap can be reduced to zero if the opposed faces of the armature Ez and electro-magnet G are required to act as braking-surfaces when the parts E T are also abutting'.

Although the springs Y extend between opposite brake-elements, there might be an abutment a such as is shown in chain-lines in the drawing, extended inward from the casing X and constituting an abutment for separate springs which might then be considered as formed by two separated halves of the original spring Y. The advantage of the construction which employs a sin le spring between the two `coned brakeee ements is that it enables a long spring to be used; the two coned brake-elements are not in practice operated upon simultaneously, and consequently therefore when either one of them is used, it utilizes the whole length of the spring which at such time rests against the other as an abutment.l

In Fig. 2 the aforesaid springs Y are dispensed with, and the brake-element U, such as is employed in Fig. 1, is adjustable lengthwise of the casing X, kept from rotating therein as in Fig. 1, and is held in lts lengthwise position by an adjusting-device Z2 which is a rotatably screwed spindle held from endwse movement in a hole in the end of the casing X by the stud S and iange f, and engaging by the screw-threaded portion p of the spindle a tapped hole in the part U.

Although in the foregoing description T and Ea have coned coperated surfaces, the advantages of the invention with regard to the convenience of adjustment of the parts T, E3 and E2 in company in relation to the electro-magnet G would remain if the surfaces of the parts T and E3 were radial to the axis of the shafts A1 and A instead of conical.

What I claim as my invention and desire to secure by Letters Patent is zl. In a bevel-wheel electro-magnetic epicyclic speed changing gear of the class described, the combination of two non-rotating circular brake elements, springs bearing on the two elements to thrust them away from one another, regulating stops to regulate the position to which said springs can move the brake elements, fixed electro-magnets, bevel sun gears, and armature elements, and friction surface elements turnin with said bevel sun gears, and springs ten ing to 'friction surface elements turnin keep said elements away from the electro circular brake-element, a rotatable screw in Y i threaded engagement with it to adjust it toward and away from its support, means which are situated in the support and engage said rotatable screw to prevent the latter from moving lengthwise, a xed electromagnet, and a rotatable armature element and rotatable friction-surface element that turns with the said rotatable armature-element. f

4:. In a bevel-Wheel electro-magnetic epicyclic speed-changing gear of the class described, the combination of two non-rotat' ing circular conical brake elements, springs bearing at their opposite -ends on the two elements to thrust them away from one another, regulating screw stops to regulate the position to which said springs can move the brake elements, fixed electro-magnets, bevel sun gears, and armature elements, and coned with said bevel sun gears, and springs ten ing to keep said elements away from the electro-magnets.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

GEORGE POLLARD. 

